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FBI investigators are talking to friends, family members, and others who knew Aaron Alexis from his days in Fort Worth. (Published Tuesday, Sept. 17, 2013)

Updated at 10:53 AM PDT on Tuesday, Sep 17, 2013

A discharged Navy Petty Officer Third Class, who served at the Naval Air Station Joint Reserve Base in Fort Worth, Texas, is the suspected gunman behind Monday's mass shooting at the Navy Yard in Washington, D.C.

Alexis was arrested in Fort Worth in Sept. 2010 for discharging a firearm inside city limits, a Class A misdemeanor, Tarrant County records show. At the time, he told police he accidentally discharged the weapon while cleaning it, and he was arrested. No charges were filed.

The Tarrant County District Attorney's office released the following statement Monday regarding Alexis' arrest: "After reviewing the facts presented by the police department, it was determined that the elements constituting recklessness under Texas law were not present and a case was not filed."

Bud Kennedy Talks Experience With Alexis as Waiter

Star-Telegram restaurant critic Bud Kennedy talked with NBC 5 about his experience meeting Aaron Alexis while the suspected gunman was working at a local Thai restaurant. (Published Tuesday, Sept. 17, 2013)

NBCDFW has learned Alexis served four years in the Navy after enlisting in New York in May 2007. He graduated from boot camp at Great Lakes, Ill., as an airman recruit, and served for four years.

He eventually became an aviation electrician's mate, a Petty Officer Third Class, who served on active duty at the Naval Air Station Joint Reserve Base in Fort Worth until he was discharged on Jan. 31, 2011. While enlisted, Alexis received the National Defense Service Medal and the Global War on Terrorism Service Medal.

During his time in Fort Worth, Alexis was taken in by a family who owned a Thai restaurant near the air base. They remembered Alexis as a peaceful man who helped out at the restaurant as well as a nearby Buddhist temple where he was said to be a practicing member.

One friend who spoke with NBCDFW said the only red flags he could think of were that Alexis may have been upset that a contractor had been slow to pay him for a job he'd worked in Japan and that, even though he was good-natured, he spent a lot of time playing violent video games.

Suspected Navy Yard Gunman's Fort Worth Ties

Aaron Alexis, the suspected gunman in a mass shooting at the Washington Navy Yard, has ties to Fort Worth, including a run-in with the Fort Worth Police Department. (Published Tuesday, Sept. 17, 2013)

"I saw the video games just the one time, and when I did, I was like, 'I can't believe you play that stuff.' It was like shooting, you know, where you're shooting them, they're shooting you," said friend Michael Ritrovato.

Officials at the NASJRB are referring all comments regarding Alexis' service history to Washington.

NBC 5 visited the last known Fort Worth address for Alexis on Monday night. When our crew knocked on the door at about 7:30 p.m., they were greeted by a man identifying himself as an FBI agent.

Alleged Gunman in Navy Yard Shooting Has FW Ties

The FBI came to Fort Worth Monday to check out the last known residence of Aaron Alexis, the man authorities have identified as the gunman in the mass shooting at the Navy Yard in Washington, D.C. Monday. Meanwhile details about Alexis' s past continue to emerge. (Published Monday, Sept. 16, 2013)

An hour later, two FBI agents and two people believed to be the homeowners left the residence in separate vehicles. The two people believed to be the homeowners did not respond to questions.

When asked if the interviews were complete, one of the FBI agents responded, "Not yet." The homeowner is believed to be one of the last people to see Alexis in Texas.

According to the 2010 arrest report from Fort Worth, Alexis' upstairs neighbor called police after a hearing a pop and seeing a cloud of dust come up from her floor; she said a bullet had ripped through her floor and ceiling from the apartment downstairs.

Alexis' North Texas Connection

A profile of Aaron Alexis, the man who authorities identified as the gunman in the deadly mass shooting at the Navy Yard in Washington, D.C., is emerging. Alexis was enlisted in the Navy, a defense contractor and converted to Buddhism, but he also had run-ins with police over shootings in Fort Worth and Seattle. (Published Monday, Sept. 16, 2013)

Fort Worth police knocked on her neighbor's door, but there was no answer. As they prepared to enter through force, the man, identified as Alexis, came outside and talked with police willingly. He said he had been cleaning his weapon when it slipped and that he accidentally pulled the trigger.

He said he didn't check on his neighbor because he couldn't see light through the hole in his ceiling and assumed the bullet hadn't passed through her floor. He also said he thought his neighbors would assume the sound of the gunshot was a firecracker.

According to police, Alexis told them he didn't answer the door initially because he assumed it was his upstairs neighbor, with whom he shared a contentious relationship.

2004 Arrest in Seattle Due to "Anger-Fueled" Shooting

Dramatic Photos: DC Navy Yard Shooting

Seattle police said Monday afternoon that Alexis was arrested in 2004 "for shooting out the tires of another man’s vehicle in what Alexis later described to detectives as an anger-fueled 'blackout.'"

In the incident report, Seattle police said Alexis exited his apartment and pulled a handgun from his waistband before firing three rounds at the rear tires of a car that belonged to a man working construction in the area. Alexis eventually confessed to the shooting, but stated that the man had mocked him after learning his own vehicle had been tampered with and that the shooting was an "anger-fueled blackout" that he didn't recall until an hour after the shooting. He was eventually booked into the King County Jail on a charge of malicious mischief.

According to the Seattle Police Department, during his interview regarding the shooting, Alexis told them he was present during the "tragic events of September 11, 2001" and "described 'how those events had disturbed him.'"

Police eventually talked with Alexis' father, who lived in New York, and said his son had anger problems related to Post Traumatic Stress Disorder and that he was "an active participant in rescue attempts on September 11th, 2001."

While in Washington, D.C., Alexis had begun working as a civilian contractor for the Navy, according to NBC's Pete Williams.

The FBI said Monday night that contrary to earlier reports, as a contractor Alexis had access the heavily secured building at the yard. Alexis used a valid pass to gain entry to Building 197, where most of the victims were shot on the third and fourth floors.

According to Washington, D.C. Police Chief Cathy Lanier police are have eliminated the possibility of another suspect in the shooting and have lifted the shelter-in-place order. "We do now feel comfortable that we have the single and sole person responsible," Lanier said Monday night.

Washington D.C.'s Mayor Vincent Gray said the victims killed Monday ranged in age from 46 to 73 years of age.

The Metropolitan Police Department released the names of seven of the 13 killed Monday:

"We do know that several people have been shot, and some have been killed," President Barack Obama said. "So we are confronting yet another mass shooting, and today it happened on a military installation in our nation’s capital. It's a shooting that targeted military and civilian personnel. These are men and women going to work, doing their job protecting all of us. They're patriots, and they know the dangers of serving abroad, but today they faced the unimaginable violence that they wouldn’t have expected here at home."

Initial reports indicated that Aaron Alexis was enlisted as a reservist during his four years of service in the U.S. Navy. An NBC 5 source confirmed Monday afternoon that Alexis was on active duty from 2007 to 2011. We regret the error.